I think a lot of people tuned in to watch all those (semi) famous people in the cameos get eaten by sharks or killed in some other gruesome way.
snip-
Ziering: “There were so many people clamoring for cameos in this movie. That was a tough thing for the director and the writer to decide. Who were we going to let be eaten? Everyone wanted to be eaten. It seems like it’s a badge of honor to have that on your IMDb account when it says “Man #2 eaten in ‘Sharknado.’”
http://www.foxnews.com/entertainment/2014/07/30/sharknado-star-ian-ziering-sharknado-3-is-go/
Sure was awesome to see Robert Hays ( Airplane ) as a pilot once again.